Added an option to limit max size in files_recv

The default is set to 100MB, which means pushing
larger files will stop when reaches this limit.
This limit can be adjusted by file_recv_max_size
option in the master's config file.
file_recv_max_size config is specified in megabyte
Merge pull request #9108 from pakdel/file_recv_max_size

Added an option to limit maximum size of a file that can be pushed to master by files_recv